At this time there is a critical national need for removing toxic compounds from groundwater, surface water and industrial waste waters without transferring these compounds to the atmosphere or to burial sites. At present, oxidation by incineration or chemical means is the only method of accomplishing true detoxification rather than mere displacement of these organic toxicants into the atmosphere or to another medium.
Incineration of dilute aqueous solutions of organic components is costly due to the energy required for the evaporation of water. Moreover, incineration may cause the formation of toxic by-products, such as dioxin derivatives, in the off-gases. Chemical oxidation processes to treat contaminated water include use of such substances as for example, potassium permanganate, chlorine dioxide, chlorine, hydrogen peroxide, or ozone. Additionally, oxidation may be enhanced using ultraviolet light (UV) in conjunction with any of these substances except permanganate.
Chemical detoxification methods are in commercial use for wastewaters and some ground waters. These methods present attendant disadvantages, however. For example, potassium permanganate produces manganese dioxide as a by-product during oxidation. Chlorine, and in some instances, chlorine dioxide, forms chlorinated organic compounds. Moreover, hydrogen peroxide plus ferrous sulfate (Fenton's reagent) produces soluble and insoluble iron residues.
Ozonation without UV light partially oxidizes benzene derivatives to mono- and di-basic acids which are biodegradable, but does not oxidize saturated halogenated compounds. Oxidation with hydrogen peroxide and UV light is useful for oxidizing a number of organic compounds, but in many cases the rates of oxidation are significantly slower than when using UV/03. While ozone combined with UV enhancement has been found to be cost-effective and practical for non-volatile unsaturated chlorinated hydrocarbons and a number of benzene derivatives, certain saturated chlorinated and oxygenated compounds, such as the pervasive pollutants methylene chloride and methanol, have been found to be refractory to UV-ozonation.
In addition certain types of fuels, such as rocket fuels, contain hydrazine and hydrazine derivatives including monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH) as well as mixtures of these compounds. During the course of procurement, storage, transport and testing of such hydrazine fuels, there is a possibility for environmental contamination, for example of water sources. Therefore, there is a need for treatment technologies for contaminated water generated at fuel production sites and/or from spilled fuels. The use of ozone and ultraviolet light to treat aqueous solutions containing hydrazine, MMH and UDMH has been investigated. (Sierka et al., Report September 1978, Civil and Environmental Engineering Development Office, (CEEDO), Tyndall Air Force Base, Fla.; and Jody et al., "Oxidation of Hydrazines and Their Associated Impurities", available from the Aerospace Corporation, Los Angeles, Calif.).
The toxicity and carcinogenicity of most compounds with a N-nitroso (N-N=0) structure is well established (Druckery et al., Krebsforsch, 69:103 (1967); Ember, Chemical and Engineering News, 58:20 (1980); and Tsai-Hi et al., J. Agr. Food Chem., 19:1267 (1971)). Nitrosamines, one group of N-nitroso compounds, are formed when amines react with nitrogen oxides and/or nitrite ions (Ember, supra). Because of ready availability of precursors, presumably (CH.sub.3).sub.2 N.multidot. and partially oxidized nitrogen species such as NO.sub.2 --, NO and NO.sub.2, dimethylnitrosamine, (DMNA) one of the more potent carcinogens in various animal species, can be formed as an intermediate during oxidation of UDMH and to a much lesser extent during oxidation of MMH. (Judeikis, "Modeling the Ozonolysis at Hydrazine Wastewater", available from the Aerospace Corporation, Los Angeles, Calif.) has proposed a general mechanism applicable to the ozonation of hydrazine derivatives concluding that oxidation of DMNA, which reaches the maximum level just as the parent hydrazines are no longer detectable, spears to be the rate limiting step in the overall ozonation of hydrazine derivatives. Because DMNA is more resistant than the parent compound (UDMH) to oxidation it persists in the solution of oxidized UDMH solutions after the parent compound has been completely destroyed.
Thus, there is a long standing need for powerful and practical methods for removing a wide spectrum of toxic compounds from water. Such a method should provide both a highly effective and cost-effective means of detoxifying hazardous compounds. The present application fulfills these needs and provides related advantages as well.